As a technology for detecting an AC input voltage, there has been known a technology a technology for detecting an AC input voltage using a photocoupler, for example.
However, in a method of detecting an AC input voltage using a photocoupler, it is possible to appropriately detect an AC input voltage, but the power consumption of a light emitting diode of the photocoupler is not negligible. Accordingly, a technology for detecting an AC input voltage that can save electric power has been eagerly desired.